Sitting is the most frequent body posture: we sit at work, at school, in the car, on the bus, on the train, in an airplane, and so on. Those who are wheelchair-bound are in sitting positions for entire days.
A seat should take the weight off one's feet in order to lessen stress on the legs, and the seat should provide some postural stability while one works or relaxes. One should also be able to relax muscles that are at rest.
The seat height should not be so high that the occupant's legs are left dangling. This would mean that there would be pressure on the soft tissues under the thighs. This pressure can interfere with the return of blood from the lower limbs, which may cause tingling and numbness in the thighs due to pressure on blood vessels and nerves.
At the same time, there exists an opinion that prolonged travel in a sitting position can cause venous stasis. Venous stasis refers to loss of proper function of the veins in the legs that would normally carry blood back to the heart.
N. S. Lee, et al, showed in their “Review of Selected Literature Related to Seating Discomfort” submitted in 1990 to Ikeda Engineering Corporation, MI, USA that in terms of ml/min/100 ml of body segment, blood flow in the leg of a person (4 ml/min/100 ml) in a seated position is much lower than, e.g., in the arm (10 ml/min/100 ml). This means that the legs of a seated person are to a greater extent subject to phenomenon such as tingling and numbness in the thighs caused by pressure on blood vessels and nerves.
It is understood that in the body of a person seated on a chair or on a similar support, the aforementioned abnormalities of blood circulation are caused by areas on the chair that cause increased pressure on the thighs. In the majority of cases, such areas are the edges of a seat.
Attempts have been made to improve a seat support for redistribution of pressure on the buttocks. For example, Pain Releiver Co., KS, distributes a G-Seat Gel Cushion [hereinafter referred to as the “G-Seat Gel Seat Cushion” below] for improved blood circulation. (See Http://www.autosportcatalog.com/index.cfm/fa/p/pid/2168/cid/57/sc/2737)
The G-Seat Gel Seat Cushion uses viscoelastic gel and a functional design to disperse pressure and improve the level of comfort wherever one sits. The “G-Seat Gel Cushion” features a center relief groove that eliminates soft-tissue compression and suspends the tailbone (coccyx), which eliminates direct pressure on the spine.
Pressure redistribution occurs because the gel that fills the seat works like a liquid and takes the form of the conforming body part, i.e., the buttocks. In other words, the pressure on the buttock and thigh surfaces that are in contact with the G-seat is redistributed in accordance with Pascal's Law, i.e., in a normal direction and essentially uniformly in all points of contact. However, since the G-seat is substantially flat, the problem is solved only partially. In other words, localized areas of increased pressure will still exist on the boundaries of the G-seat.
German Patent Publication DE10200500243 published Jul. 27, 2006 (inventor A. Wunder, et al) discloses a chair with a seat that has a backrest, cushion, and an adjustable thigh support. The thigh support comprises a U-shaped unit that is arranged across the chair under the thighs of the occupant and is adjustable opposite to the cushion. A gap is formed between the cushion and the U-shaped unit during adjustment of the U-shaped unit opposite to the cushion. The gap is coverable by an adjustment device, and the cushion is composed of a foam material.
The above-described thigh support does not solve the aforementioned problem of localized pressure on the thigh surfaces at the edge of the transverse thigh support and, instead, only shifts the position of the edge.
A number of patents, such as U.S. Pat. No. 4,636,002 (published Jan. 13, 1987, inventor T. Genjiro); U.S. Pat. No. 4,712,834 (published Dec. 15, 1987, inventor J. Warrick, et al); and U.S. Pat. No. 4,838,509 (published Jun. 13, 1989, inventor J. Klink, et al), etc., disclose car seats with adjustable features that include thigh supports. However, all of these devices are permanently built into the structure of the seat, are driven with the use of complicated and expansive mechanisms, and change only the vertical and angular positions of the transverse thigh support.
The applicant of the present patent application has made an attempt to improve the ergonomics of a driver's seat (see pending U.S. patent application Ser. No. 11/509,376 of Aug. 24, 2006).
The aforementioned invention provides a thigh support and restrainer for use in combination with a driver's car seat. The device is made in the form of a triangular pad that is attached to the car seat cushion and supports the driver's leg in a position required for minimal time needed for movement of the driver's foot from the accelerator pedal to the brake pedal at the moment of danger. The pad is provided with straps that can be wrapped around the driver's right thigh for restraining the driver's leg in the aforementioned position of the minimal time for reaching the brake pedal. For optimization of the position of the thigh support on the driver's seat, the support is provided with straps which are attached to the seat and have means for securing the thigh support in a selected position. Another pending U.S. patent application Ser. No. 11/515,192 filed by the same applicant in 2006 relates to a method and device for finding a position of the seat support most optimal from the viewpoint of shortening the time required for the driver to push on a brake pedal after the driver is confronted with an obstacle.
Although the thigh support of the aforementioned patent perfectly fulfills its function of shortening the time require for braking, it has a specific use and only partially solves the problem of uniformity of pressure distribution on the thigh surface in contact with the driver's seat.